Self-adaptive zero-carbon power generation system utilizing LNG (Liquefied Natural Gas) cold energy and flue gas waste heat

Abstract

The invention discloses a self-adaptive zero-carbon power generation system utilizing LNG (Liquefied Natural Gas) cold energy and flue gas waste heat, belongs to the fields of LNG cold energy utilization technology, industrial waste gas treatment, waste heat recovery and CO2 capture, and solves the problems that the efficiency of LNG cold energy and flue gas waste heat recovery in the prior art is low, flue gas is difficult to effectively treat to reduce environmental pollution, and the like. And the power generation system is easily influenced by factors such as LNG flow fluctuation and cannot stably operate. According to the self-adaptive zero-carbon power generation system, the self-adaptive zero-carbon power generation system is constructed, the LNG cold energy power generation circulation line and the waste heat recovery line cooperatively operate, the LNG cold energy and the flue gas waste heat are utilized, flue gas is treated for emission reduction through multi-stage working medium heat exchange and expansion acting, and efficient energy utilization and environment friendliness are achieved. According to the system, LNG cold energy and flue gas waste heat are utilized for efficient power generation, and the energy utilization rate is increased. And flue gas is synchronously and deeply treated, pollution emission is reduced, the system is stabilized by a cold storage medium, and efficient, environment-friendly and stable operation is realized.

Description

Technical Field

[0001] The present invention relates to the fields of LNG cold energy utilization technology, industrial waste gas treatment waste heat recovery and CO2 capture technology, and in particular to an adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat. Background Art

[0002] Liquefied natural gas (LNG) is a normal-pressure liquid formed by purifying natural gas and cooling it to -162°C. Before reaching the user, it needs to be heated and vaporized to approximately 25°C, releasing approximately 830 kJ / kg of cold energy. However, most LNG receiving stations currently release this cold energy directly into seawater or air, resulting in significant cold energy waste.

[0003] Current methods for utilizing LNG cold energy include cold power generation, alkane separation, dry ice production, and cold water aquaculture. Cold power generation, with its advantages of low safety risks and high energy quality, has attracted extensive research from experts and scholars. Current methods for utilizing LNG cold power generation primarily include direct vaporization and expansion (DC), single-stage organic Rankine cycle (ORC), and multi-stage organic Rankine cycle (ORC). All current LNG cold power generation methods require stable cold input from the LNG cooling source. However, domestic LNG receiving stations are primarily peak-shaving, resulting in significant fluctuations in output. This, in turn, leads to significant fluctuations in the cooling source in the cold power generation system, resulting in poor system stability and hindering the widespread application of cold power generation. Existing solutions involve designing LNG storage tanks at the front end of the cold power generation process, but this increases LNG storage costs and poses safety risks. Furthermore, existing LNG cold power generation methods only consider LNG as the front-end cooling source and fail to consider the coupled utilization of LNG cold energy through waste gas and waste heat recovery after natural gas combustion.

[0004] See Chinese patent document CN106150578A (publication date: November 23, 2016), which discloses a multi-stage coupled LNG cold energy utilization cycle power generation system. This system utilizes a three-stage cycle process, with only the third stage using seawater as the heat source. This results in a lower initial temperature and pressure for the third-stage circulating medium at the turbine inlet, resulting in a smaller enthalpy difference between the turbine inlet and outlet. Furthermore, because the first stage is powered by the condensation heat released by the second stage, and the second stage by the condensation heat released by the third stage, the net power generation of both the first and second stages is low, resulting in a low overall power generation output. When the LNG inlet pressure is 0.6-7 MPa and the mass flow rate is 3600 kg / h, the net power generation per ton of LNG is 66.5-29.74 kWh. Furthermore, when the LNG leaves the system, its temperature is still between -53°C and -47°C, and this portion of the cold energy is unutilized.

[0005] Chinese patent document CN115614118B (publication date: January 17, 2023) discloses a cascade-coupled cold energy recovery and utilization system for liquefied natural gas (LNG). The system includes a primary, secondary, and tertiary cold energy generation subsystems for organic Rankine cycle power generation, a fourth-stage cold energy utilization subsystem for organic Rankine cycle power generation or cold storage refrigeration and ice making, and a fifth-stage cold energy generation subsystem for direct gasification and expansion power generation. The primary, third, and fourth-stage cold energy utilization subsystems are connected in parallel, one after another, while the secondary and primary cold energy generation systems are connected in series, achieving cascade-coupled recovery and utilization of LNG cold energy. This system requires an LNG storage tank at the front end to provide a stable LNG cold source with a mass flow rate of 150 t / h, which increases the system's natural gas storage costs.

[0006] Chinese patent document CN115749978B (publication date: 2023-03-07) discloses a power generation system that utilizes LNG cold energy and industrial waste heat recovery. The system uses high-temperature flue gas generated by coking and steel rolling processes and circulating water from steelmaking and ironmaking as heat sources. Although industrial waste heat is utilized, the system does not achieve the recovery and capture of water and carbon dioxide in the flue gas of the steel plant.

[0007] The current LNG cold energy power generation system only considers LNG as the cold source of the power generation system, and does not consider the low-grade natural gas in other stages of the natural gas industry chain as the heat source; in the process of utilizing LNG cold energy, it does not consider using cold energy to reduce carbon emissions in the natural gas industry chain; at the same time, the current LNG cold energy power generation system has high requirements for the stability of LNG flow, and the power generation and power generation efficiency are highly dependent on the LNG flow at the cold end. Summary of the Invention

[0008] The present invention proposes an adaptive zero-carbon power generation system that utilizes LNG cold energy and flue gas waste heat, which can realize cascade cold storage and thus realize adaptive LNG flow changes of the front-end cold source to reduce the storage cost of LNG and the storage pressure of LNG storage tanks; the system utilizes the flue gas waste heat from natural gas combustion and the cascade utilization of LNG cold energy to achieve efficient power generation; the system also utilizes LNG cold energy to separate and capture carbon dioxide in the flue gas to achieve zero carbon emissions of natural gas flue gas, thereby solving the problems existing in the prior art.

[0009] An adaptive zero-carbon power generation system that utilizes LNG cold energy and flue gas waste heat, including:

[0010] The primary and secondary cold energy power generation cycle circuits are used to realize steam extraction heat recovery Rankine cycle power generation, the waste heat recovery circuit is used to realize flue gas waste heat recovery, the LNG circuit is used to gasify LNG into gaseous natural gas, and the flue gas treatment circuit is used to realize natural gas combustion flue gas cleaning treatment and carbon dioxide capture;

[0011] The primary cold energy power generation cycle circuit, the secondary cold energy power generation cycle circuit and the flue gas treatment circuit are connected in series step by step through the LNG circuit.

[0012] Furthermore, the first-stage cold energy power generation cycle includes an LNG-first circulating working fluid cold storage heat exchanger, a No. 1 first working fluid pump, a No. 1 first regenerator, a No. 2 first working fluid pump, a No. 2 first regenerator, a No. 3 first working fluid pump, a third circulating working fluid-first circulating working fluid heat exchanger, a first working fluid expander, a first-stage steam extraction heat recovery branch, a second-stage steam extraction heat recovery branch, and a first working fluid power generation branch, wherein,

[0013] The inlet of the first working fluid expander is connected to the outlet of the third circulating working fluid-first circulating working fluid heat exchanger, the first outlet of the first working fluid expander is connected to the inlet of the first stage extraction steam heat recovery branch, the outlet of the first stage extraction steam heat recovery branch is connected to the first inlet of the No. 2 first heat regenerator, and the outlet of the No. 2 first heat regenerator is connected to the inlet of the No. 3 first working fluid pump;

[0014] The second outlet of the first working fluid expander is connected to the inlet of the second-stage steam extraction heat regeneration branch, the outlet of the second-stage steam extraction heat regeneration branch is connected to the first inlet of the No. 1 first regenerator, the outlet of the No. 1 first regenerator is connected to the inlet of the No. 2 first working fluid pump, and the outlet of the No. 2 first working fluid pump is connected to the second inlet of the No. 2 first regenerator;

[0015] The third outlet of the first working fluid expander is connected to the inlet of the LNG-first circulating working fluid cold storage heat exchanger, the outlet of the LNG-first circulating working fluid cold storage heat exchanger is connected to the inlet of the first working fluid power generation branch for power generation, the outlet of the first working fluid power generation branch for power generation is connected to the inlet of the No. 1 first working fluid pump, and the outlet of the No. 1 first working fluid pump is connected to the second inlet of the No. 1 first reheater.

[0016] Furthermore, the secondary cold energy power generation cycle includes an LNG-second circulating working fluid cold storage heat exchanger, a No. 1 second working fluid pump, a No. 1 second regenerator, a No. 2 second working fluid pump, a No. 2 second regenerator, a No. 3 second working fluid pump, a third circulating working fluid-second circulating working fluid heat exchanger, a second working fluid expander, a first-stage steam extraction heat recovery branch, a second-stage steam extraction heat recovery branch, and a second working fluid power generation branch, wherein,

[0017] The outlet of the third circulating working fluid-second circulating working fluid heat exchanger is connected to the inlet of the second working fluid expander, the first outlet of the second working fluid expander is connected to the inlet of the first stage extraction steam heat recovery branch, the outlet of the first stage extraction steam heat recovery branch is connected to the first inlet of the No. 2 second heat regenerator, the outlet of the No. 2 second heat regenerator is connected to the inlet of the No. 3 second working fluid pump, and the outlet of the No. 3 second working fluid pump is connected to the inlet of the third circulating working fluid-second circulating working fluid heat exchanger;

[0018] The second outlet of the second working fluid expander is connected to the inlet of the second-stage steam extraction heat regeneration branch, the outlet of the second-stage steam extraction heat regeneration branch is connected to the first inlet of the No. 1 second regenerator, the outlet of the No. 1 second regenerator is connected to the inlet of the No. 2 second working fluid pump, and the outlet of the No. 2 second working fluid pump is connected to the second inlet of the No. 2 second regenerator;

[0019] The third outlet of the second working fluid expander is connected to the inlet of the LNG-second circulating working fluid cold storage heat exchanger, the outlet of the LNG-second circulating working fluid cold storage heat exchanger is connected to the inlet of the second working fluid power generation branch for power generation, the outlet of the second working fluid power generation branch for power generation is connected to the inlet of the No. 1 second working fluid pump, and the outlet of the No. 1 second working fluid pump is connected to the second inlet of the No. 1 second regenerator.

[0020] Furthermore, the waste heat recovery circuit includes a third working fluid pump, a flue gas-third cycle working fluid heat exchanger, a third cycle working fluid-second cycle working fluid heat exchanger and a third cycle working fluid-first cycle working fluid heat exchanger, wherein:

[0021] The waste heat recovery working fluid is introduced into the inlet of the heat exchanger, and the outlet of the heat exchanger is connected with the inlet of the third working fluid pump. The outlet of the third working fluid pump is respectively connected with the waste heat recovery working fluid inlet of the third circulation working fluid-second circulation working fluid heat exchanger and the waste heat recovery working fluid inlet of the third circulation working fluid-first circulation working fluid heat exchanger. Both the third circulation working fluid-second circulation working fluid heat exchanger and the third circulation working fluid-first circulation working fluid heat exchanger are provided with waste heat recovery working fluid outlets.

[0022] Furthermore, the LNG line includes an LNG pump, an LNG-first circulating medium cold storage heat exchanger, an LNG-second circulating medium cold storage heat exchanger, an NG-dehydrated flue gas heat exchanger, an NG-flue gas heat exchanger, and a seawater-NG heat exchanger, wherein:

[0023] Liquefied natural gas is introduced into the inlet of the LNG pump, and the inlet of the LNG pump is connected with the liquefied natural gas inlet of the LNG-first circulating medium cold storage heat exchanger, and the liquefied natural gas outlet of the LNG-first circulating medium cold storage heat exchanger is connected with the liquefied natural gas inlet of the LNG-second circulating medium cold storage heat exchanger, and the liquefied natural gas outlet of the LNG-second circulating medium cold storage heat exchanger is connected with the liquefied natural gas inlet of the NG-dehydrated flue gas heat exchanger, and the liquefied natural gas outlet of the NG-dehydrated flue gas heat exchanger is connected with the liquefied natural gas inlet of the NG-flue gas heat exchanger, and the liquefied natural gas outlet of the NG-flue gas heat exchanger is connected with the liquefied natural gas inlet of the seawater-NG heat exchanger, and the liquefied natural gas outlet of the seawater-NG heat exchanger is connected with the user end.

[0024] Furthermore, the flue gas treatment circuit includes a flue gas-third cycle working medium heat exchanger, an NG-flue gas heat exchanger, a flue gas-ice separator, a multi-stage compressor, an LNG-dehydrated flue gas heat exchanger, a dehydrated flue gas-liquid carbon dioxide separator, a cooling tank, a heating tank, a multi-stage expansion stage and a compensation circuit, wherein,

[0025] The waste heat flue gas inlet of the heat exchanger introduces the waste heat flue gas caused by natural gas combustion, the normal temperature flue gas outlet of the heat exchanger is connected to the normal temperature flue gas inlet of the heat exchanger, the dehydrated flue gas outlet of the heat exchanger is connected to the dehydrated flue gas inlet of the multi-stage compressor, the high-pressure flue gas outlet of the multi-stage compressor is connected to the high-pressure flue gas inlet of the cooling tank, the medium-temperature flue gas outlet of the cooling tank is connected to the thermal measurement inlet of the heat exchanger, the thermal measurement outlet of the heat exchanger is connected to the gas-liquid mixed inlet of the separator, the liquid CO2 outlet of the separator is independently connected to the CO2 storage tank, the residual gas outlet of the separator is connected to the residual gas inlet of the multi-stage expander, the expanded gas outlet of the multi-stage expander is connected to the low-temperature gas inlet of the heating tank, and the qualified exhaust port of the heating tank is connected to the atmosphere.

[0026] In the compensation circuit, the multi-stage expander serves as an electric energy output device, and the electric energy generated by the expander is preferentially supplied to the multi-stage compressor serving as an electric energy input device.

[0027] Furthermore, in the first-level cold energy power generation cycle,

[0028] The LNG-first cycle working medium cold storage heat exchanger is used to use the cold energy of LNG to cool the first cycle working medium, condense the first cycle working medium into saturated liquid, and at the same time recover the cold energy of the liquid phase of LNG. When the LNG flow rate is too large, the excess cold energy is stored in the cold storage medium; when the flow rate is too small, the stored cold energy is released to cool the exhaust steam after the first working medium expander does work;

[0029] The No. 1 first working fluid pump is used to pressurize the saturated liquid working fluid from the LNG-first circulating working fluid cold storage heat exchanger, increase the working fluid pressure, and provide power for the circulating working fluid to circulate in the system;

[0030] The No. 1 first regenerator is used to preheat the working fluid output from the No. 1 first working fluid pump by exchanging heat with the superheated steam with lower pressure extracted from the second-stage extraction steam heat recovery branch, thereby increasing the working fluid temperature and recovering the heat of the extraction steam;

[0031] The No. 2 first working fluid pump is used to further pressurize the working fluid after being preheated by the No. 1 first regenerator, so that the working fluid pressure meets the requirements for entering the No. 2 first regenerator and subsequent circulation, and maintain the circulating pressure of the working fluid in the system;

[0032] The No. 2 first regenerator is used to exchange heat with the high-pressure superheated steam extracted from the first-stage extraction steam regeneration branch, preheating the working fluid output from the No. 2 first working fluid pump and increasing the initial temperature of the working fluid. At the same time, the extraction steam is cooled at a constant pressure in the No. 2 first regenerator and completely condensed.

[0033] The No. 3 first working fluid pump is used to re-pressurize the working fluid after being preheated by the No. 2 first regenerator to ensure that the working fluid can smoothly enter the third circulation working fluid-first circulation working fluid heat exchanger;

[0034] The third circulating working medium-first circulating working medium heat exchanger is used to recover the working medium by utilizing waste heat. It heats the first circulating working medium pressurized by the No. 3 first working medium pump into superheated steam, thereby increasing the energy quality of the working medium and preparing it for expansion and work in the first working medium expander.

[0035] A first working medium expander is used to expand the superheated steam in the first working medium expander to perform work, converting the internal energy of the steam into mechanical energy to drive the generator to generate electricity. During the expansion process, part of the steam is extracted from different positions for heat recovery;

[0036] The first-stage extraction steam regeneration branch is used to extract a portion of the superheated steam with a relatively high pressure from the first working medium expander and introduce it into the No. 2 first regenerator for constant pressure cooling and complete condensation. The released heat is used to preheat the first circulating working medium after it is mixed with the second-stage extraction steam regeneration branch and the first working medium power generation branch.

[0037] The second-stage steam extraction heat recovery branch is used to extract a portion of superheated steam with a lower pressure from the first working medium expander and enter the No. 1 first regenerator for constant pressure cooling and complete condensation. The released heat is used to preheat the condensed first circulating working medium in the first working medium power generation branch, further improving the thermal efficiency of the system;

[0038] The first working medium power generation branch is used to allow the remaining first circulating working medium after the first working medium expander performs work to continue to participate in the circulation through the first working medium power generation branch;

[0039] In the secondary cold energy power generation cycle,

[0040] The LNG-secondary working medium cold storage heat exchanger is used to cool the secondary working medium using the latent heat energy of the LNG gas-liquid phase change, condensing the secondary working medium into a saturated liquid, thereby recycling the cold energy of the LNG latent heat segment. When the LNG flow rate is too large, the excess cold energy is stored in the cold storage medium. When the flow rate is too small, the stored cold energy is released to cool the exhaust steam after the secondary working medium expander has done work.

[0041] The No. 1 second working fluid pump is used to pressurize the saturated liquid working fluid flowing out of the LNG-second circulating working fluid cold storage heat exchanger, increase the working fluid pressure, and provide power for the subsequent circulation of the working fluid in the system, so that it can smoothly enter the next equipment No. 1 second regenerator;

[0042] The No. 1 second regenerator is used to exchange heat with the superheated steam at a lower pressure extracted from the second-stage extraction heat recovery branch. On the one hand, it recovers the heat of this steam to improve energy utilization efficiency. On the other hand, it uses the recovered heat to preheat the second circulating working fluid output from the No. 1 second working fluid pump to increase the working fluid temperature.

[0043] The second working fluid pump No. 2 is used to further pressurize the second circulating working fluid after being preheated by the second regenerator No. 1, so that the working fluid pressure meets the requirements for entering the second regenerator No. 2 and subsequent circulation, and maintain the circulating pressure of the working fluid in the system;

[0044] The No. 2 second regenerator is used to exchange heat with the high-pressure superheated steam extracted from the first-stage extraction heat recovery branch, recovering the heat of this steam and using it to preheat the second circulating working fluid output from the No. 2 second working fluid pump, further increasing the initial temperature of the working fluid;

[0045] The No. 3 second working fluid pump is used to re-pressurize the second circulating working fluid after being preheated by the No. 2 second regenerator, ensuring that the working fluid can enter the third circulating working fluid-second circulating working fluid heat exchanger with sufficient pressure to provide pressure conditions for the subsequent heating process;

[0046] The third circulating working medium-second circulating working medium heat exchanger is used to recover the working medium by utilizing waste heat. It heats the second circulating working medium pressurized by the No. 3 second working medium pump into superheated steam, thereby increasing the energy quality of the working medium and enabling it to expand and perform work in the second working medium expander.

[0047] The second working medium expander is used to expand the hot steam in the second working medium expander to perform work, converting the internal energy of the steam into mechanical energy, thereby driving the generator to generate electricity; during the expansion process, part of the steam is extracted from different positions and introduced into the No. 2 second regenerator and the No. 1 second regenerator through the first-stage steam extraction heat recovery branch and the second-stage steam extraction heat recovery branch respectively, for preheating the second circulating working medium;

[0048] The first-stage steam extraction heat recovery branch is used to extract a portion of high-pressure superheated steam from the second working fluid expander and introduce it into the No. 2 second regenerator. In the No. 2 second regenerator, this steam is cooled at a constant pressure and completely condensed. The heat released is used to preheat the second circulating working fluid output from the No. 2 second working fluid pump;

[0049] The second-stage steam extraction heat recovery branch is used to extract a portion of superheated steam with a lower pressure from the second working fluid expander and introduce it into the No. 1 second regenerator. In the No. 1 second regenerator, the steam is cooled at a constant pressure and completely condensed. The released heat is used to preheat the second circulating working fluid output from the No. 1 second working fluid pump;

[0050] The second working medium power generation branch is used to allow the remaining second circulating working medium after the second working medium expander performs work to continue to participate in the circulation through the second working medium power generation branch;

[0051] In the waste heat recovery circuit,

[0052] The third working medium pump is used to pressurize the third circulating working medium after being heated by the flue gas-third circulating working medium heat exchanger;

[0053] The flue gas-tertiary cycle working medium heat exchanger is used to exchange heat between the high-temperature flue gas generated by natural gas combustion and the tertiary cycle working medium, heating the tertiary cycle working medium and cooling the high-temperature flue gas;

[0054] The heat exchanger is used to distribute the high-temperature third circulation working medium to the third circulation working medium-second circulation working medium heat exchanger and the third circulation working medium-first circulation working medium heat exchanger, thereby cooling the high-temperature third circulation working medium;

[0055] The third-circulation working medium-second-circulation working medium heat exchanger is also used to exchange heat between the high-temperature third-circulation working medium from the flue gas-third-circulation working medium heat exchanger and the second-circulation working medium of the secondary cold energy power generation cycle. After absorbing heat, the second-circulation working medium is heated to superheated steam, thereby increasing its energy quality, and then enters the second-circulation working medium expander to expand and perform work;

[0056] The third circulation working medium-first circulation working medium heat exchanger is also used to exchange heat between the high-temperature third circulation working medium from the flue gas-third circulation working medium heat exchanger and the first circulation working medium of the first-stage cold energy power generation cycle. After absorbing heat, the first circulation working medium is heated to superheated steam, thereby increasing its energy quality, and then enters the first working medium expander to expand and perform work;

[0057] In LNG lines,

[0058] LNG pump, used to pressurize low-temperature, low-pressure LNG;

[0059] The LNG-first circulating medium cold storage heat exchanger is also used to utilize the cold energy of the liquid phase of LNG flowing through the LNG pump to cool the first circulating medium, condensing the first circulating medium into a saturated liquid. This transfers cold energy to the first circulating medium, providing a cold source for the first-stage cold energy power generation cycle. It also has a cold energy storage function. When the LNG flow rate fluctuates, it stores excess cold energy and releases it when the LNG flow rate is insufficient, thereby stabilizing system operation.

[0060] The LNG-secondary circulating medium cold storage heat exchanger is also used to cool the secondary circulating medium using the latent heat of the LNG flowing through the LNG-primary circulating medium cold storage heat exchanger, condensing the secondary circulating medium into a saturated liquid. This transfers cold energy to the secondary circulating medium, providing a cold source for the secondary cold energy power generation cycle. It also has a cold energy storage function. When the LNG flow rate fluctuates, it stores excess cold energy and releases it when the LNG flow rate is insufficient, thereby stabilizing system operation.

[0061] NG-Flue Gas Heat Exchanger is used to achieve heat exchange between natural gas and flue gas, that is, using the heat of flue gas to heat natural gas. At the same time, the flue gas is cooled during the heat exchange process, and the water in it is cooled into solid ice, thereby removing moisture from the flue gas;

[0062] The seawater-NG heat exchanger is used to heat the natural gas using the heat of seawater, ensuring that the output natural gas can enter the user end at an appropriate temperature to meet the user's usage needs;

[0063] In the flue gas treatment line,

[0064] The flue gas-tertiary circulation working medium heat exchanger is used to recover the waste heat in the flue gas. By transferring the heat of the flue gas to the tertiary circulation working medium, the temperature of the tertiary circulation working medium is increased, thereby realizing the recovery and utilization of the waste heat and reducing the flue gas temperature at the same time;

[0065] NG-Flue gas heat exchanger is used to exchange heat between flue gas and natural gas, using the heat of flue gas to heat the natural gas, thereby increasing the temperature of the natural gas and further reducing the flue gas temperature, condensing the water vapor in the flue gas into solid ice, thereby achieving initial dehydration of the flue gas;

[0066] Flue gas-ice separator, used to separate ice particles formed in the flue gas after cooling to prevent ice particles from entering subsequent equipment;

[0067] Multi-stage compressor compresses the flue gas that has undergone preliminary treatment to increase the flue gas pressure;

[0068] LNG-dehydration flue gas heat exchanger uses the cold energy of LNG to cool the dehydrated flue gas, further cooling the carbon dioxide in the flue gas and recovering part of the cold energy in the flue gas;

[0069] Dehydrated flue gas-liquid carbon dioxide separator is used to separate the liquid carbon dioxide from the cooled flue gas to obtain relatively pure carbon dioxide;

[0070] Cooling tank is used to cool the incoming dehydrated flue gas. The cooling medium is water, and the heated water is supplied to the hot end users.

[0071] The multi-stage expansion stage is used to expand the remaining gas after the carbon dioxide is separated in the multi-stage expander to produce work. Through the expansion of the gas, the internal energy of the gas is converted into mechanical energy, thereby driving other equipment or generating electricity;

[0072] The heating tank is used to heat the remaining gas to room temperature and then discharge it into the atmosphere. The heating medium is water, and the cooled water is supplied to the cold end users.

[0073] Furthermore, the LNG-first circulating working fluid cold storage heat exchanger and the LNG-second circulating working fluid cold storage heat exchanger each include a shell, a heat transfer tube bundle, a support assembly, a cold storage medium, and a circulating working fluid. The support assembly is fixedly installed in the shell, and the heat transfer tube bundle is fixedly installed on the support assembly. The shell is filled with a cold storage medium and a circulating working fluid, and the cold storage medium is immersed in the circulating working fluid. When the flow rate of low-temperature natural gas in the heat transfer tube bundle is too large, the additional cold energy is stored in the cold storage medium. When the flow rate of low-temperature natural gas in the heat transfer tube bundle is too small, the cold energy stored in the cold storage medium is used to cool the exhaust steam after expansion and work in the expander in the cold energy power generation cycle circuit in which it is located;

[0074] The circulating working fluid in the LNG-first circulating working fluid cold storage heat exchanger is the first circulating working fluid, and the heat transfer tube bundle in the LNG-first circulating working fluid cold storage heat exchanger contains liquefied natural gas pressurized to the vaporization pressure by the LNG pump;

[0075] The circulating working fluid in the LNG-second circulating working fluid cold storage heat exchanger is the second circulating working fluid, and the heat transfer tube bundle in the LNG-second circulating working fluid cold storage heat exchanger contains natural gas that has been heated by the LNG-first circulating working fluid cold storage heat exchanger but still has a relatively low temperature;

[0076] The arrangement of heat transfer tube bundles includes but is not limited to in-line, spiral, serpentine, sleeve, and fin types;

[0077] Cold storage media include but are not limited to rock, metal, alloy or a combination of any two or three of rock, metal and alloy

[0078] Furthermore, the first circulating working fluid and the second circulating working fluid include C2H4, C2H6, C3H6, C3H8, C4H 10, CH3F, CH2F2, CHF3, C2H4F2, C2H3F3, C2H2F4, C2HF5, C2F6, C3F8 and mixtures of two or more.

[0079] Furthermore, in the first-stage cold energy power generation cycle, the steam extraction capacity is determined by the following formula:

[0080] α1(h a1 -h a1′ )=(1-α1)(h a1′ -h b1″ )

[0081] α2(h b1 -h b1′ )=(1-α1-α2)(h b1′ -h c1 )

[0082] where h a1 、h a1′ 、h b1 、h b1′ 、h b1″ 、h c1 are the enthalpy values ​​of points a1, a1′, b1, b1′, b1″, and c1, respectively, so as to obtain the extraction steam capacity α1 of the first-stage extraction steam regeneration branch:

[0083]

[0084] The extraction steam volume of the second stage extraction steam regeneration branch α2:

[0085]

[0086] Then the steam volume of the first working medium power generation branch is (1-α1-α2);

[0087] The specific steam extraction capacity of the secondary cold energy power generation cycle is determined by the following formula:

[0088] β1(h a2 -h a2′ )=(1-β1)(h a2′ -h b2″ )

[0089] β2(h b2 -h b2′ )=(1-β1-β2)(h b2′ -h c2 )

[0090] where h a2 、h a2′ 、h b2 、h b2′ 、h b2″、h c2 are the enthalpy values ​​of points a2, a2′, b2, b2′, b2″, and c2, respectively, so as to obtain the extraction steam capacity β1 of the first-stage extraction steam regeneration branch:

[0091]

[0092] The extraction steam volume of the second stage extraction steam regeneration branch β2:

[0093]

[0094] Then the steam volume of the second working medium power generation branch is (1-β1-β2).

[0095] Beneficial effects of the present invention:

[0096] 1. The present invention provides an adaptive zero-carbon power generation system that utilizes LNG cold energy and flue gas waste heat. This system, thanks to the cold storage medium 604 in the cold storage heat exchangers H1 and H2, achieves cascaded storage of LNG cold energy. When the flow rate of LNG, serving as a cold source, is too large, the additional cold energy is stored in the cold storage medium 604. When the flow rate of LNG, serving as a cold source, is too small, the cold energy stored in the cold storage medium 604 is used to cool the exhaust steam after expansion work in expanders T1 and T2. This reduces the power generation system's reliance on the stability of the cold source and lowers the storage cost of the LNG front end.

[0097] 2. The present invention is an adaptive zero-carbon power generation system that utilizes LNG cold energy and flue gas waste heat. Benefiting from the heat exchanger H7 using waste heat recovery working fluid to recover waste heat from the natural gas combustion flue gas, it is used to heat the first cycle working fluid and the second cycle working fluid to a superheated steam state, thereby increasing the enthalpy difference between the working fluid before and after the inlet and outlet of the expander, thereby improving the system's power generation and cold energy utilization rate.

[0098] 3. The adaptive zero-carbon power generation system of the present invention utilizes LNG cold energy and flue gas waste heat. Thanks to the longitudinal series connection of the first-level cold energy power generation cycle circuit and the second-level cold energy power generation cycle circuit, the cascade utilization of LNG cold energy is realized; at the same time, the expanders T1 and T2 adopt a secondary steam extraction and heat recovery setting, and a portion of steam with different pressures is extracted from different middle positions of the expander for constant pressure cooling. The heat released by condensation is used to preheat the first circulation working fluid and the second circulation working fluid after the cycle power generation, thereby increasing the average heat absorption temperature and improving the utilization rate of cold energy.

[0099] 4. The present invention employs an adaptive zero-carbon power generation system that utilizes LNG cold energy and flue gas waste heat. Benefiting from the pressurization of the multi-stage compressor MC and the cooling of the heat exchangers H3 and H4, the system removes and recovers water and carbon dioxide from the flue gas, thereby achieving zero-carbon emissions from the flue gas. Simultaneously, the multi-stage expander ME and the multi-stage compressor MC form a compensation circuit, with the electrical power of the multi-stage expander preferentially supplied to the multi-stage compressor MC, thereby reducing the flue gas treatment circuit's demand for external electrical power. BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Figure 1 This is a schematic structural diagram of an adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to the present invention;

[0101] Figure 2 Schematic diagram of steam extraction and heat recovery of the primary cold energy power generation cycle circuit and the secondary cold energy power generation cycle circuit;

[0102] Figure 3 Schematic diagram of the structure of the LNG-first circulating medium cold storage heat exchanger H1 and the LNG-second circulating medium cold storage heat exchanger H2;

[0103] Figure 4 This is a diagram illustrating the logistics components of an adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat to achieve cascade cold energy generation, flue gas waste heat recovery, and carbon dioxide capture according to an embodiment of the present invention, wherein:

[0104] LNG, LNG_1, LNG_2: liquefied natural gas;

[0105] NG, NG_1, NG_2, NG_3: natural gas;

[0106] WF1_1, WF1_2, WF1_3, WF1_4, WF1_5, WF1_6, WF1_7, WF1_8, WF1_9, WF1_10: propane;

[0107] WF2_1, WF2_2, WF2_3, WF2_4, WF2_5, WF2_6, WF2_7, WF2_8, WF2_9, WF2_10: propane;

[0108] w1, w2, w3, w4, w5, w6, w7, w8, w9, w10, w11, w12, w13: sea water;

[0109] g1, g2, g3, g4, g5, g6, g7, g8: flue gas.

[0110] Among them, 100 is the first-level cold energy power generation cycle line, 200 is the second-level cold energy power generation cycle line, 300 is the waste heat recovery line, 400 is the LNG line, 500 is the flue gas treatment line, H1 is the LNG-first cycle working fluid cold storage heat exchanger, P3 is the first working fluid pump No. 1, R2 is the first regenerator No. 1, P4 is the second first working fluid pump No. 2, R1 is the second first regenerator No. 2, P2 is the third first working fluid pump No. 3, H5 is the third cycle working fluid-first cycle working fluid heat exchanger, T1 is the first working fluid expander, 101 is the first-stage extraction steam heat recovery branch, 102 is the second-stage extraction steam heat recovery branch, 103 is the first working fluid power generation branch, H2 is the LNG-second cycle working fluid cold storage heat exchanger, P6 is the first second working fluid pump No. 1, R4 is the first second regenerator No. 1, P7 is the second second working fluid pump No. 2, R3 is the second regenerator No. 2, P5 is the third second Second working fluid pump, H6 is the third circulation working fluid-second circulation working fluid heat exchanger, T2 is the second working fluid expander, 201 is the first stage extraction steam heat recovery branch, 202 is the second stage extraction steam heat recovery branch, 203 is the second working fluid power generation branch, P8 is the third working fluid pump, H7 is the flue gas-third circulation working fluid heat exchanger, P1 is the LNG pump, H3 is the NG-dehydration flue gas heat exchanger, H4 is the NG-flue gas heat exchanger, H8 is the seawater-NG heat exchanger, S1 is the flue gas-ice separator, MC is the multi-stage compressor, H3 is the LNG-dehydration flue gas heat exchanger, S2 is the dehydration flue gas-liquid carbon dioxide separator, W1 is the cooling tank, W2 is the heating tank, ME is the multi-stage expander, 601 is the shell, 602 is the heat transfer tube bundle, 603 is the support assembly, 604 is the cold storage medium, 605 is the first circulation working fluid, and 606 is the second circulation working fluid. DETAILED DESCRIPTION

[0111] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0112] Example 1:

[0113] Figure 1 A schematic structural diagram of an adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to an embodiment of the present invention is shown for realizing cascaded cold energy power generation, flue gas waste heat recovery, and carbon dioxide capture.

[0114] Among them, the first-level cold energy power generation circulation circuit 100, the second-level cold energy power generation circulation circuit 200 and the flue gas treatment circuit 500 are connected in series step by step through the LNG line 400. The LNG flows through the first-level cold energy power generation circulation circuit, the second-level cold energy power generation circulation circuit and the flue gas treatment circuit in sequence, and exchanges heat with the first circulating working fluid and cold storage medium in the cold storage heat exchanger H1, the second circulating working fluid and cold storage medium in the cold storage heat exchanger H2, the dehydrated flue gas in the heat exchanger H3, and the flue gas in the heat exchanger H4 in sequence, thereby increasing the temperature of the natural gas and ensuring that the temperature of the vaporized natural gas meets the user-end requirements.

[0115] The specific first-stage cold energy power generation cycle circuit 100 includes an LNG-first circulating working fluid cold storage heat exchanger H1, a No. 1 first working fluid pump P3, a No. 1 first regenerator R2, a No. 2 first working fluid pump P4, a No. 2 first regenerator R1, a No. 3 first working fluid pump P2, a third circulating working fluid-first circulating working fluid heat exchanger H5, a first working fluid expander T1, a first-stage extraction steam heat recovery branch 101, a second-stage extraction steam heat recovery branch 102, and a first working fluid power generation branch 103;

[0116] The secondary cold energy power generation cycle 200 includes the LNG-second circulating working fluid cold storage heat exchanger H2, the No. 1 second working fluid pump P6, the No. 1 second regenerator R4, the No. 2 second working fluid pump P7, the No. 2 second regenerator R3, the No. 3 second working fluid pump P5, the third circulating working fluid-second circulating working fluid heat exchanger H6, the second working fluid expander T2, as well as the first-stage extraction steam heat recovery branch 201, the second-stage extraction steam heat recovery branch 302, and the power generation second working fluid power generation branch 203;

[0117] The waste heat recovery circuit 300 includes a third working medium P8, a flue gas-third cycle working medium heat exchanger H7, a third cycle working medium-second cycle working medium heat exchanger H6, and a third cycle working medium-first cycle working medium heat exchanger H5.

[0118] The LNG line 400 includes an LNG pump P1, an LNG-first circulating medium cold storage heat exchanger H1, an LNG-second circulating medium cold storage heat exchanger H2, an NG-dehydrated flue gas heat exchanger H3, an NG-flue gas heat exchanger H4, and a seawater-NG heat exchanger H8;

[0119] The flue gas treatment circuit 500 includes a flue gas-third cycle working medium heat exchanger H7, an NG-flue gas heat exchanger H4, a flue gas-ice separator S1, a multi-stage compressor MC, an LNG-dehydration flue gas heat exchanger H3, a dehydrated flue gas-liquid carbon dioxide separator S2, a multi-stage expansion stage ME, and a compensation circuit between the ME and MC;

[0120] The working process of an adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to an embodiment of the present invention is as follows:

[0121] After being pressurized to vaporization pressure by LNG pump P1, liquefied natural gas (LNG) flows sequentially through the LNG-first circulating working fluid cold storage heat exchanger H1, the LNG-second circulating working fluid cold storage heat exchanger H2, the NG-dehydrated flue gas heat exchanger H3, the flue gas-NG heat exchanger H4, and the seawater-NG heat exchanger H8, absorbing heat and vaporizing to a temperature suitable for downstream users. The cold storage heat exchanger H1 recovers cold energy from the LNG's latent heat phase, the cold storage heat exchanger H2 recovers cold energy from the LNG's low-temperature gas phase, and the heat exchangers H3, H4, and H8 recover cold energy from the natural gas's high-temperature gas phase. In this order, the natural gas is heated to a temperature suitable for downstream users.

[0122] In the first-stage cold energy power generation cycle 100, the first circulating working medium is pressurized by the pump P2, heated to superheated steam through the heat exchanger H5, and then expanded and worked in the expander T1. A portion of the superheated steam with a higher pressure is extracted from the expander through the branch 101 and enters the No. 2 first regenerator R1 for constant pressure cooling and complete condensation to preheat the first circulating working medium mixed with the branch 102 and 103; then a portion of the superheated steam with a lower pressure is extracted from the expander T1 through the branch 102 and enters the No. 1 first regenerator R2 for constant pressure cooling. Cooling, complete condensation, and preheating of the first circulating working fluid after condensation in branch 103; the remaining first circulating working fluid is completely expanded and performs work in expander T1, and the expanded gas-liquid mixture enters the cold storage heat exchanger H1 for heat exchange and condensation into saturated liquid, passes through pump P3, enters the No. 1 first regenerator R2 from branch 103, and is mixed with the first circulating working fluid cooled and condensed in branch 102, passes through pump P4, enters the No. 2 first regenerator R1, and is mixed with the first circulating working fluid cooled and condensed in branch 101 for heat exchange, and then enters the next cycle through pump P2.

[0123] Specific extraction steam heat recovery Figure 2 As shown, the specific extraction steam volume is determined by the following formula:

[0124] α1(h a1 -h a1′ )=(1-α1)(h a1′ -h b1″ )

[0125] α2(h b1 -h b1′ )=(1-α1-α2)(h b1′ -h c1 )

[0126] Thus, the steam extraction amount α1 of branch 101 is obtained:

[0127]

[0128] Extraction steam volume α2 of branch 102:

[0129]

[0130] Then the steam volume of branch 103 is (1-α1-α2);

[0131] Specific first cycle working fluids include but are not limited to C2H4, C2H6, C3H6, C3H8, C4H 10 , CH3F, CH2F2, CHF3, C2H4F2, C2H3F3, C2H2F4, C2HF5, C2F6, C3F8 and mixtures of two or more.

[0132] The specific LNG-first cycle working medium cold storage heat exchanger H1 is as follows: Figure 3 As shown, the shell 601, heat transfer tube bundle 602 and support assembly 603 are filled with cold storage medium 604 and first circulating working medium 605. The heat transfer tube bundle 602 contains liquefied natural gas pressurized to the vaporization pressure by pump P1. The heat transfer tube bundle 602 is fixed to the support assembly 603, and the cold storage medium 604 is immersed in the first circulating working medium 605.

[0133] The cold storage medium 604 includes but is not limited to various rocks such as limestone and granite, and metals and alloys such as steel blocks and iron blocks;

[0134] Specifically, in the cold storage heat exchanger H1, the liquefied natural gas pressurized to the vaporization pressure by the pump P1 enters the heat transfer tube bundle through the tube inlet of the cold storage heat exchanger H1 and exchanges heat with the cold storage medium 604 and the first circulating working medium 605 filled inside the shell; the cold storage is when the flow rate of LNG as the cold source is too large, the additional cold energy is stored in the cold storage medium 604; when the flow rate of LNG as the cold source is too small, the cold energy stored in the cold storage medium 604 is used to cool the exhaust steam after expansion and work in the expander T1.

[0135] In the secondary cold energy power generation cycle 200, the second circulating working medium is pressurized by the pump P5, heated to superheated steam by the heat exchanger H6, and then expanded and worked in the expander T2. A portion of the superheated steam with a higher pressure is extracted from the expander through the branch 201 and enters the second regenerator R3 of the second unit for constant pressure cooling and complete condensation to preheat the second circulating working medium mixed with the branch 202 and 203; and a portion of the superheated steam with a lower pressure is extracted from the expander through the branch 202 and enters the second regenerator R4 of the first unit for constant pressure cooling. The second circulating working fluid after condensation in the preheating branch 203 is cooled and completely condensed; the remaining second circulating working fluid is completely expanded and does work in the expander T2, and the expanded gas-liquid mixture enters the cold storage heat exchanger H2 for heat exchange and condensation into a saturated liquid. After passing through pump P6, it enters the No. 1 second regenerator R4 from branch 203 and is mixed with the second circulating working fluid cooled and condensed in branch 202. After passing through pump P4, it enters the No. 2 second regenerator R3 and is mixed with the second circulating working fluid cooled and condensed in branch 201 for heat exchange and enters the next cycle through pump P5.

[0136] Similar to the primary cold energy power generation cycle circuit 100, the specific steam extraction amount of the secondary cold energy power generation cycle circuit 200 is determined by the following formula:

[0137] β1(h a2 -h a2′ )=(1-β1)(h a2′ -h b2″ )

[0138] β2(h b2 -h b2′ )=(1-β1-β2)(h b2′ -h c2 )

[0139] Thus, the steam extraction amount β1 of branch 201 is obtained:

[0140]

[0141] Extraction steam volume β2 of branch 202:

[0142]

[0143] Then the steam volume of branch 203 is (1-β1-β2);

[0144] Specific second cycle working fluids include but are not limited to C2H4, C2H6, C3H6, C3H8, C4H 10 , CH3F, CH2F2, CHF3, C2H4F2, C2H3F3, C2H2F4, C2HF5, C2F6, C3F8 and mixtures of two or more.

[0145] Specifically, the LNG-secondary circulating working medium cold storage heat exchanger H2 consists of a shell 601, a heat transfer tube bundle 602, and a support assembly 603. The shell is filled with cold storage medium 604 and secondary circulating working medium 605. The heat transfer tube bundle 602 contains natural gas that has been heated by the cold storage heat exchanger H1 but still has a relatively low temperature. The heat transfer tube bundle is fixed to the support assembly 603, and the cold storage medium 604 is immersed in the secondary circulating working medium 605.

[0146] Specific cold storage media 604 include, but are not limited to, rocks such as limestone, granite, and dolomite, metals such as steel, iron, aluminum, and copper, and alloys such as stainless steel, iron-nickel alloy, copper-nickel alloy, and iron-cobalt alloy;

[0147] Specifically, in the cold storage heat exchanger H2, the natural gas that has been heated by the cold storage heat exchanger H1 but still has a relatively low temperature enters the heat transfer tube bundle through the tube inlet of the cold storage heat exchanger H2 and undergoes heat exchange with the cold storage medium 604 and the second circulating working medium 605 filled inside the shell; the cold storage is when the flow rate of low-temperature natural gas in the tube is too large, the additional cold energy is stored in the cold storage medium 604; when the flow rate of low-temperature natural gas in the tube is too small, the cold energy stored in the cold storage medium 604 is used to cool the exhaust steam after expansion and work in the expander T2.

[0148] In the waste heat recovery circuit 300, the waste heat recovery medium enters the heat exchanger H7 to be heated, is pressurized by the pump P8, and enters the separator S3 for separation. A portion enters the heat exchanger H6 to be cooled, and the other portion enters the heat exchanger H5 to be cooled. The outlets of the heat exchangers H5 and H6 are the cooled waste heat recovery medium.

[0149] Specifically, water is preferably used as the working medium for waste heat recovery, and the cooled water can be supplied to cold-end users.

[0150] In LNG line 400, liquefied natural gas (LNG) is pressurized to vaporization pressure by LNG pump P1 and then flows sequentially through LNG-first circulating working fluid cold storage heat exchanger H1, LNG-second circulating working fluid cold storage heat exchanger H2, NG-dehydrated flue gas heat exchanger H3, flue gas-NG heat exchanger H4, and seawater-NG heat exchanger H8, where it absorbs heat and vaporizes to a temperature suitable for downstream users. Cold storage heat exchanger H1 recovers cold energy from the latent heat of LNG, cold storage heat exchanger H2 recovers cold energy from the low-temperature gas phase of LNG, and heat exchangers H3, H4, and H5 recover cold energy from the high-temperature gas phase of natural gas. In this order, the natural gas is heated to a temperature suitable for downstream users.

[0151] In the flue gas treatment circuit 500, the waste heat flue gas caused by the combustion of natural gas passes through the heat exchanger H7 and is cooled to room temperature gas. It then passes through the heat exchanger H4 and is cooled to below zero, and the water in the flue gas is cooled into solid ice. After passing through the separator S1, the low-temperature gas with the solid ice removed enters the multi-stage compressor MC. The dehydrated flue gas is compressed to high pressure by the multi-stage compressor MC, and the pressurized dehydrated flue gas enters the cooling tank W1 and is cooled. After passing through the heat exchanger H3, it is cooled to approximately -20°C, and the carbon dioxide in the dehydrated flue gas is liquefied. After passing through the separator S2, the liquid carbon dioxide is separated from the gaseous remaining gas. The remaining gas enters the multi-stage expander ME to expand and perform work. The expanded gas enters the heating tank W2, is heated to room temperature, and is discharged into the atmosphere.

[0152] Specifically, the cooling tank W1 is filled with a cooling medium, preferably water, and the heated water can be supplied to the hot end user;

[0153] Specifically, the cooling tank W2 is filled with a heating medium, preferably water, and the cooled water can be supplied to the cold end user;

[0154] The specific residual gas is mainly composed of nitrogen and oxygen;

[0155] Specifically, the multi-stage expander ME and the multi-stage compressor MC form a compensation circuit; in the compensation circuit, the work generated by the multi-stage expander ME is preferentially supplied to the multi-stage compressor MC.

[0156] The following is a further explanation of the effectiveness of an adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to an embodiment of the present invention based on a specific example:

[0157] Specific example 1:

[0158] Assume that the LNG gasification scale used in this adaptive zero-carbon power generation system that utilizes LNG cold energy and flue gas waste heat is 150 tons per hour. LNG is directly extracted from a peak-shaving LNG receiving station. The incoming LNG temperature is -162°C, the pressure is 0.1MPa, and the mass flow rate is unstable. Assume that the mass flow rate variation range is 150t (±10%) t / h, the pressure requirement for long-distance natural gas pipeline transportation is 7MPa, and the temperature of LNG after gasification by this system is required to be no less than 5°C. In this specific example, the initial temperature of seawater used as the waste heat recovery working fluid is 15°C, and the initial temperature of the natural gas combustion flue gas is 150°C. The specific components are shown in Table 1:

[0159] Element Mole fraction (mol%) water 26.08 carbon dioxide 6.52 Nitrogen 63.55 oxygen 3.85

[0160] Table 1 Composition of natural gas combustion flue gas

[0161] First, when the LNG inflow mass flow rate remains stable at 150t / h, the system is The embodiment of the present invention is an adaptive zero-carbon power generation system using LNG cold energy and flue gas waste heat to achieve cascade cold energy generation and flue gas waste heat recovery and carbon dioxide capture. The specific logistics components are as follows: Figure 4 shown.

[0162] Among them, LNG reaches a vaporization pressure of 7MPa and a temperature of -160℃ after being pressurized by LNG pump P1. It enters the LNG-first circulating working fluid cold storage heat exchanger H1 in the first-level cold energy power generation cycle circuit for heat exchange and is heated to -95℃. It then enters the LNG-second circulating working fluid cold storage heat exchanger H2 in the second-level cold energy power generation cycle circuit for heat exchange and is heated to -55℃. It then enters the LNG-dehydrated flue gas heat exchanger H3 for heat exchange and is heated to -38℃. It then enters the flue gas-NG heat exchanger H4 for heat exchange and is heated to -6℃. Finally, it enters the flue gas-NG heat exchanger H8 for heat exchange and is heated to 5℃.

[0163] First-stage cold energy power generation cycle: Assume that the first circulating working fluid in the first-stage cold energy power generation cycle is propane. Propane expands and performs work in expander T1. Superheated propane vapor (α1 = 15.7%) at a pressure of 275.51 kPa and a temperature of -10°C is extracted from expander T1 through branch 101 and enters the No. 2 first regenerator R1 for constant pressure cooling and complete condensation to preheat the propane mixed with branches 102 and 103. Then, propane vapor (α2 = 14.1%) at a pressure of 70.56 kPa, a temperature of -50°C and a dryness of 98.05% is extracted from the expander through branch 102 and enters the No. 1 first regenerator R2 for constant pressure cooling and complete condensation to preheat the condensed propane in branch 103. The remaining propane vapor (1-α1-α2) = 70.2% is then extracted from the expander. After the complete expansion and work in expander T1, the exhaust steam pressure at the end of expansion is 6.44 kPa, the temperature is -90°C, and the dryness is 90.4%. This portion of the propane gas-liquid mixture enters the LNG-first circulating working medium cold storage heat exchanger H1, where it is cooled and condensed into a saturated liquid; it is then pressurized to 70.56 kPa by pump P3, enters the No. 1 first regenerator R2 through branch 103, mixes with the propane cooled and condensed in branch 102, is pressurized to 275.51 kPa by pump P4, enters the No. 2 first regenerator R1, mixes with the propane cooled and condensed in branch 101, and is pressurized to 1 MPa by pump P2. It then enters the heat exchanger H5, where it is heated to 40°C and enters the next cycle.

[0164] The cold storage heat exchanger H1 consists of a shell, a heat transfer tube bundle, and a support assembly. The heat transfer tube bundle contains pressurized low-temperature LNG and is fixed to the support assembly. The inside of the shell is filled with limestone and immersed in propane.

[0165] The interior of the cold storage heat exchanger H1 is a cylindrical space with a diameter of 15m and a height of 10m. The limestone particles filled in it have an average diameter of 20mm, an average porosity of 40%, and a filling ratio of 80%. The thermophysical properties of the limestone are shown in Table 2:

[0166]

[0167] Table 2 Physical properties of various rocks

[0168] The mass of limestone filled in the cold storage heat exchanger H1 is:

[0169] m stone =π×7.5 2 ×10×80%×(1-40%)×2740=2324.1t

[0170] When the system is running stably, the propane and limestone in the cold storage heat exchanger H1 maintain a stable temperature of -90°C. The physical properties of the propane at this time are shown in Table 3:

[0171]

[0172] Table 3 Physical properties of propane at various temperatures

[0173] At this time, the mass of propane filled in the cold storage heat exchanger H1 is:

[0174] m propane =π×7.5 2 ×10×80%×40%×633.32=358.13t

[0175] Secondary cold energy power generation cycle: Assume that the second circulating working fluid in the secondary cold energy power generation cycle is propane. The propane expands and performs work in expander T2. β1 = 8% of the superheated propane vapor at a pressure of 275.51 kPa and a temperature of -10°C is extracted from expander T2 via branch 201 and enters the second regenerator R3 for constant pressure cooling and complete condensation to preheat the propane mixed in branches 202 and 203. β2 = 8% of the superheated propane vapor at a pressure of 155.38 kPa and a temperature of -30°C is then extracted from the expander via branch 202 and enters the second regenerator R4 for constant pressure cooling and complete condensation to preheat the condensed propane in branch 203. The remaining (1-β1-β2) = 84% of the propane vapor is fully expanded in expander T2. After doing work, the exhaust steam pressure at the end of expansion is 70.56 KPa, the temperature is -50°C, and the dryness is 98.05%. This part of the propane gas-liquid mixture enters the LNG-second cycle working medium cold storage heat exchanger H2, is cooled and condensed into a saturated liquid; then it is pressurized to 155.38 KPa by pump P6, enters the No. 1 second regenerator R4 through branch 103, and is mixed with the propane cooled and condensed in branch 202, and is then pressurized to 275.51 KPa by pump P7, enters the No. 2 second regenerator R3, and is mixed with the propane cooled and condensed in branch 201, and is then pressurized to 1 MPa by pump P5, enters the heat exchanger H6, is heated to 40°C, and enters the next cycle.

[0176] The cold storage heat exchanger H2 consists of a shell, a heat transfer tube bundle, and a support assembly. The heat transfer tube bundle contains pressurized low-temperature LNG and is fixed to the support assembly. The inside of the shell is filled with limestone and immersed in propane.

[0177] Similar to the cold storage heat exchanger H1, the cold storage heat exchanger H2 has a cylindrical space with a diameter of 15m and a height of 10m. The average diameter of the limestone particles filled is 20mm, the average porosity is 40%, and the filling ratio is 80%.

[0178] The mass of limestone filled in the cold storage heat exchanger H2 is:

[0179] m stone =π×7.5 2 ×10×80%×(1-40%)×2740=2324.1t

[0180] When the system is running stably, the propane and limestone in the cold storage heat exchanger H2 maintain a stable temperature of -50°C. At this time, the mass of the propane filled in the cold storage heat exchanger H1 is:

[0181] m propane =π×7.5 2 ×10×80%×40%×633.32=358.13t

[0182] Flue gas zero carbon treatment line: the waste heat flue gas caused by the combustion of natural gas with a temperature of 150℃ and a pressure of 101.5KPa passes through the heat exchanger H7 and is cooled to 20℃; then passes through the heat exchanger H4 and is cooled to -10℃, and the water in the flue gas is cooled into solid ice; after passing through the separator S1, the low-temperature gas with a temperature of -10℃ and a pressure of 101.5KPa after the solid ice is removed enters the multi-stage compressor MC; after being compressed once by the multi-stage compressor MC into a high-temperature and high-pressure gas with a temperature of 125℃ and a pressure of 431KPa, it passes through the cooling tank W1 and is cooled to a low-temperature and high-pressure gas of 35℃ and a pressure of 412KPa, and then is compressed twice by the multi-stage compressor MC into a high-temperature and high-pressure gas with a temperature of 125℃ and a pressure of 940KPa, and then passes through the cooling tank W1 and is cooled to a low-temperature and high-pressure gas of 35℃ and a pressure of 412KPa. The flue gas is a low-temperature, high-pressure gas of 910KPa, which is compressed three times by the multi-stage compressor MC to a high-temperature, high-pressure gas of 125℃ and a pressure of 2172KPa, and then passed through the cooling tank W1 to be cooled to a low-temperature, high-pressure gas of 35℃ and a pressure of 2100KPa; it enters the heat exchanger H3 to be cooled to a gas of -20℃ and a pressure of 2025KPa, and the carbon dioxide in the flue gas is liquefied; after passing through the separator S2, the liquid carbon dioxide is separated from the gaseous remaining gas; the remaining gas enters the multi-stage expander ME and is expanded once to a low-temperature, low-pressure gas of -43℃ and a pressure of 1395KPa, which is heated by the heating tank W2 to a normal-temperature, low-pressure gas of 5℃ and a pressure of 1326KPa. This is repeated four times to expand to a normal-temperature, normal-pressure gas of 5℃ and a pressure of 101KPa for discharge.

[0183] The cooling medium of cooling tank W1 is preferably water, which is room temperature water at 15°C and 101.3KPa at the inlet. The high temperature gas at the outlet of multi-stage compressor MC is heated in stages to high temperature water at 100°C and 101.3KPa, which can be used by hot end users.

[0184] The cooling medium in the heating tank W2 is preferably water, which is room temperature water at 15°C and 101.3KPa at the inlet. The low-temperature gas at the outlet of the multi-stage expander ME is cooled in stages to low-temperature water at 10°C and 101.3KPa, which can be used by cold-end users and can be used for cold water aquaculture, etc.

[0185] Waste heat recovery line: Normal temperature water at 15°C and a pressure of 101KPa enters the heat exchanger H7 and is heated to high temperature water at 50°C and a pressure of 101KPa. It is pressurized to 300KPa by pump P7 and passes through separator S3. It flows through heat exchangers H6 and H5 respectively and is cooled to 10°C before being discharged. This low-temperature water can be used by cold-end users and can be used for cold water aquaculture, etc.

[0186] In this specific example, the temperature difference between the pinch point of all heat exchangers and condensers is greater than or equal to 5°C, the adiabatic efficiency of the expander is 0.8, and the heat loss and friction loss of all components and connections of the system are ignored. loss.

[0187] Calculations show that when the LNG inflow is stable at 150t / h, the propane flow in the first-level cold energy power generation cycle is 114t / h, and the propane flow in the second-level cold energy power generation cycle is 116t / h. 14t / h of 100°C high-temperature water can be generated to supply hot-end users and 1950t / h of cold water 10°C below ambient temperature can be supplied to cold-end users. At the same time, 160t / h of flue gas can be processed, and 28.3t / h of ice and 17.3t / h of carbon dioxide can be captured.

[0188] The power generation capacity of the expander T1 in the first-stage cold energy power generation circuit is W T1 The power generation capacity of the expander T2 in the secondary cold energy power generation circuit is W T2 The power of pumps P1 to 7 are W respectively. P1 To W P7 The power of the multi-stage compressor MC in the flue gas zero carbon treatment line is W MC , the power of the multi-stage compressor ME is W ME , the total power generation is:

[0189] W net =W T1 +W T2 +W ME -W P1 -W P2 -W P3 -W P4 -W P5 -W P6 -W P7 -W MC

[0190] The enthalpy of the LNG stream is H LNG , the enthalpy of natural gas is H NG , then the cooling capacity released before and after LNG gasification is:

[0191] Q LNG =H LNG -H NG_4

[0192] The cooling capacity provided by the system is defined as:

[0193] Q C =(H w4 -H w5 )+(H w6 -H w7 )+(Hw10 -H w11 )+(H w12 -H w13 )

[0194] The heat provided by the system is defined as:

[0195] Q H =H w9 -H w8

[0196] LNG entering the system The value is E LNG NG The value is E NG_4 , then the system The efficiency is:

[0197]

[0198] The power generation system The efficiency is:

[0199]

[0200] The cooling energy utilization rate of the system is:

[0201]

[0202] According to the above formula, the power generation system power is 9096kw, the net power generation system power is 2886kW, and the LNG and NG-1 The value difference is 9203.75kW, LNG and NG-4 The difference is 26516.25kW, and the power generation system is calculated to be The efficiency is 46.77%. The cooling capacity released before and after LNG vaporization is 31,193kW, and the system cooling energy utilization rate is 64%. It can also capture 17.3t / h of carbon dioxide and produce 28.3t / h of ice.

[0203] In this specific example, the composition of LNG in the system is shown in Table 4:

[0204] Element Mole fraction (mol%) methane 92.11 Ethane 4.17 Propane 2.43 Isobutane 0.54 n-butane 0.55 Isopentane 0.2

[0205] Table 4 Specific components of LNG

[0206] The parameters of each LNG logistics component in this specific example are shown in Table 5:

[0207]

[0208] Table 5 Parameters of logistics components

[0209] The parameters of each first circulating medium WF1 logistics component in this specific example are shown in Table 6:

[0210]

[0211]

[0212] Table 6 Parameters of the first circulating medium WF1 logistics components When the system operates stably, the propane and the limestone filled in the cold storage heat exchanger H1 maintain a stable temperature of -90°C. The parameters of the second circulating medium WF2 logistics components in this specific example are shown in Table 7:

[0213]

[0214] Table 7 Parameters of the first circulating medium WF2 logistics components When the system operates stably, the propane and limestone in the cold storage heat exchanger H2 maintain a stable temperature of -50°C. The parameters and composition of each flue gas logistics component in this specific example are shown in Table 8:

[0215]

[0216]

[0217] Table 8 Parameters and composition of each flue gas stream component The parameters and composition of each water stream in this specific example are shown in Table 9:

[0218]

[0219] Table 9 Water flow parameters

[0220] As a novel LNG cold energy utilization process system, the embodiment of the present invention utilizes the cold energy of natural gas and the waste heat of combustion flue gas through a cold, heat and electricity coupling. Its power generation system is not only more efficient than the organic Rankine cycle in the existing technology that uses seawater as a heat source, but also recycles and utilizes the waste heat in the natural gas combustion flue gas, and recovers and captures the water and carbon dioxide therein, realizing a zero-carbon, high-efficiency and green design concept.

[0221] In addition, the self-adaptation is reflected in that when the incoming LNG flow is large, the mass flow rate is 150 (+10%) t / h or equal to 165 t / h, in the cold storage heat exchanger H1:

[0222] m LNG (h LNG_2 -h LNG_1 )=m WF1 (h WF1_3 -h WF1_4 )+ΔQ1

[0223] ΔQ1 is the cold stored by the limestone and propane in the cold storage heat exchanger H1, ignoring the temperature difference between the filled limestone and the immersed propane:

[0224] ΔQ1=m stone c p_stone ΔT+m propane c p_propane ΔT

[0225] According to the above calculation, ΔT = 0.9°C. At this time, the temperature of WF1_4 drops to -90.9°C. The propane parameters at this time are shown in Table 10:

[0226] Table 10 Propane parameters of the primary power generation system when the LNG flow rate increases by 10%

[0227] In the cold storage heat exchanger H2:

[0228] m LNG (h NG_1 -h LNG_2 )=m WF2 (h WF2_3 -h WF2_4 )+ΔQ2

[0229] ΔQ2 is the cold stored by the limestone and propane in the cold storage heat exchanger H2, ignoring the temperature difference between the filled limestone and the immersed propane:

[0230] ΔQ2=m stone c p_stone ΔT+m propane c p_propane ΔT

[0231] According to the above calculation, ΔT = 1.1°C. At this time, the temperature of WF2_4 drops to -51.1°C. The propane parameters at this time are shown in Table 11:

[0232]

[0233]

[0234] Table 11 Propane parameters of the secondary power generation system when the LNG flow rate increases by 10%

[0235] At this time, the power generation system generated 9231kw, an increase of 1.5% compared to the power generation at stable flow.

[0236] In addition, the self-adaptation is reflected in that when the incoming LNG flow is small, the mass flow rate is 150 (-10%) t / h or equal to 135 t / h, in the cold storage heat exchanger H1:

[0237] m LNG (h LNG_2-h LNG_1 )=m WF1 (h WF1_3 -h WF1_4 )+ΔQ1

[0238] ΔQ1 is the cold stored by the limestone and propane in the cold storage heat exchanger H1, ignoring the temperature difference between the filled limestone and the immersed propane:

[0239] ΔQ1=m stone c p_stone ΔT+m propane c p_propane ΔT

[0240] According to the above calculation, ΔT = -1°C. At this time, the temperature of WF1_4 rises to -89°C. The propane parameters at this time are shown in Table 12:

[0241]

[0242]

[0243] Table 12 Propane parameters of the primary power generation system when the LNG flow rate decreases by 10%

[0244] In the cold storage heat exchanger H2:

[0245] m LNG (h NG_1 -h LNG_2 )=m WF2 (h WF2_3 -h WF2_4 )+ΔQ2

[0246] ΔQ2 is the cold stored by the limestone and propane in the cold storage heat exchanger H2, ignoring the temperature difference between the filled limestone and the immersed propane:

[0247] ΔQ2=m stone c p_stone ΔT+m propane c p_propane ΔT

[0248] According to the above calculation, ΔT = -1.2°C. At this time, the temperature of WF2_4 rises to -48.8°C. The propane parameters at this time are shown in Table 13:

[0249]

[0250] Table 13 Propane parameters of the secondary power generation system when the LNG flow rate decreases by 10%

[0251] At this time, the power generation system generates 8968kw of power, which is 1.4% less than the power generation at a stable flow rate.

[0252] The cold storage heat exchangers H1 and H2 in the embodiment of the present invention store the additional cold energy when the LNG flow rate is too high through the cold storage medium inside the heat exchanger, and release this part of the cold energy to cool the circulating medium when the LNG flow rate is too low, thereby ensuring the stable operation of the power generation system and the back-end system. According to the above-mentioned relevant calculations, the cold storage heat exchangers H1 and H2 of the present invention can achieve: when the LNG flow rate changes by ±10%, the electric power of the power generation system can be controlled to within a change of approximately ±1.5%, thereby realizing the system's self-adaptation between LNG flow rate and power generation.

[0253] While the specific embodiments of the present invention have been described in detail above, these are intended to be exemplary only, and the present invention is not limited thereto. Any equivalent modifications or substitutions to the present invention that would be apparent to those skilled in the art are also within the scope of the present invention. Therefore, any equivalent modifications or substitutions made without departing from the spirit and scope of the present invention are intended to be encompassed within the scope of the present invention.

Claims

1. An adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat, characterized in that: include: A primary cold energy power generation cycle circuit (100) and a secondary cold energy power generation cycle circuit (200) for realizing steam extraction heat recovery Rankine cycle power generation, a waste heat recovery circuit (300) for realizing flue gas waste heat recovery, an LNG circuit (400) for gasifying LNG into gaseous natural gas, and a flue gas treatment circuit (500) for realizing natural gas combustion flue gas cleaning treatment and carbon dioxide capture; The primary cold energy power generation cycle circuit (100), the secondary cold energy power generation cycle circuit (200) and the flue gas treatment circuit (500) are connected in series step by step through the LNG circuit (400).

2. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 1 is characterized in that: The first-stage cold energy power generation cycle (100) comprises an LNG-first cycle working fluid cold storage heat exchanger (H1), a No. 1 first working fluid pump (P3), a No. 1 first regenerator (R2), a No. 2 first working fluid pump (P4), a No. 2 first regenerator (R1), a No. 3 first working fluid pump (P2), a third cycle working fluid-first cycle working fluid heat exchanger (H5), a first working fluid expander (T1), a first-stage steam extraction heat recovery branch (101), a second-stage steam extraction heat recovery branch (102), and a first working fluid power generation branch (103), wherein: The inlet of the first working medium expander (T1) is connected to the outlet of the third circulating working medium-first circulating working medium heat exchanger (H5), the first outlet of the first working medium expander (T1) is connected to the inlet of the first stage steam extraction heat recovery branch (101), the outlet of the first stage steam extraction heat recovery branch (101) is connected to the first inlet of the second first regenerator (R1), and the outlet of the second first regenerator (R1) is connected to the inlet of the third first working medium pump (P2); The second outlet of the first working fluid expander (T1) is communicated with the inlet of the second-stage steam extraction heat recovery branch (102), the outlet of the second-stage steam extraction heat recovery branch (102) is communicated with the first inlet of the first regenerator (R2), the outlet of the first regenerator (R2) is communicated with the inlet of the second first working fluid pump (P4), and the outlet of the second first working fluid pump (P4) is communicated with the second inlet of the second first regenerator (R1); The third outlet of the first working fluid expander (T1) is connected to the inlet of the LNG-first circulating working fluid cold storage heat exchanger (H1), the outlet of the LNG-first circulating working fluid cold storage heat exchanger (H1) is connected to the inlet of the first working fluid power generation branch (103), the outlet of the first working fluid power generation branch (103) is connected to the inlet of the first working fluid pump (P3), and the outlet of the first working fluid pump (P3) is connected to the second inlet of the first regenerator (R2).

3. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 2 is characterized in that: The secondary cold energy power generation cycle circuit (200) comprises an LNG-second cycle working fluid cold storage heat exchanger (H2), a No. 1 second working fluid pump (P6), a No. 1 second heat regenerator (R4), a No. 2 second working fluid pump (P7), a No. 2 second heat regenerator (R3), a No. 3 second working fluid pump (P5), a third cycle working fluid-second cycle working fluid heat exchanger (H6), a second working fluid expander (T2), a first-stage steam extraction heat regeneration branch (201), a second-stage steam extraction heat regeneration branch (202), and a second working fluid power generation branch (203), wherein: The outlet of the third circulating working medium-second circulating working medium heat exchanger (H6) is connected to the inlet of the second working medium expander (T2), the first outlet of the second working medium expander (T2) is connected to the inlet of the first stage steam extraction heat recovery branch (201), the outlet of the first stage steam extraction heat recovery branch (201) is connected to the first inlet of the second heat exchanger (R3), the outlet of the second heat exchanger (R3) is connected to the inlet of the third second working medium pump (P5), and the outlet of the third second working medium pump (P5) is connected to the inlet of the third circulating working medium-second circulating working medium heat exchanger (H6); The second outlet of the second working fluid expander (T2) is communicated with the inlet of the second-stage steam extraction heat recovery branch (202), the outlet of the second-stage steam extraction heat recovery branch (202) is communicated with the first inlet of the first second regenerator (R4), the outlet of the first second regenerator (R4) is communicated with the inlet of the second second working fluid pump (P7), and the outlet of the second second working fluid pump (P7) is communicated with the second inlet of the second second regenerator (R3); The third outlet of the second working fluid expander (T2) is connected to the inlet of the LNG-second circulating working fluid cold storage heat exchanger (H2), the outlet of the LNG-second circulating working fluid cold storage heat exchanger (H2) is connected to the inlet of the second working fluid power generation branch (203), the outlet of the second working fluid power generation branch (203) is connected to the inlet of the No. 1 second working fluid pump (P6), and the outlet of the No. 1 second working fluid pump (P6) is connected to the second inlet of the No. 1 second regenerator (R4).

4. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 3 is characterized in that: The waste heat recovery circuit (300) includes a third working medium pump (P8), a flue gas-third circulating working medium heat exchanger (H7), a third circulating working medium-second circulating working medium heat exchanger (H6), and a third circulating working medium-first circulating working medium heat exchanger (H5), wherein: A waste heat recovery working medium is introduced into the inlet of the heat exchanger (H7), the outlet of the heat exchanger (H7) is connected to the inlet of the third working medium pump (P8), and the outlet of the third working medium pump (P8) is respectively connected to the waste heat recovery working medium inlet of the third circulation working medium-second circulation working medium heat exchanger (H6) and the waste heat recovery working medium inlet of the third circulation working medium-first circulation working medium heat exchanger (H5). Both the third circulation working medium-second circulation working medium heat exchanger (H6) and the third circulation working medium-first circulation working medium heat exchanger (H5) are provided with a waste heat recovery working medium outlet.

5. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 4 is characterized in that: The LNG line (400) includes an LNG pump (P1), an LNG-first circulating medium cold storage heat exchanger (H1), an LNG-second circulating medium cold storage heat exchanger (H2), an NG-dehydrated flue gas heat exchanger (H3), an NG-flue gas heat exchanger (H4), and a seawater-NG heat exchanger (H8), wherein: Liquefied natural gas is introduced into the inlet of the LNG pump (P1), and the inlet of the LNG pump (P1) is connected to the liquefied natural gas inlet of the LNG-first circulating medium cold storage heat exchanger (H1), the liquefied natural gas outlet of the LNG-first circulating medium cold storage heat exchanger (H1) is connected to the liquefied natural gas inlet of the LNG-second circulating medium cold storage heat exchanger (H2), the liquefied natural gas outlet of the LNG-second circulating medium cold storage heat exchanger (H2) is connected to the liquefied natural gas inlet of the NG-dehydration flue gas heat exchanger (H3), the liquefied natural gas outlet of the NG-dehydration flue gas heat exchanger (H3) is connected to the liquefied natural gas inlet of the NG-flue gas heat exchanger (H4), the liquefied natural gas outlet of the NG-flue gas heat exchanger (H4) is connected to the liquefied natural gas inlet of the seawater-NG heat exchanger (H8), and the liquefied natural gas outlet of the seawater-NG heat exchanger (H8) is connected to the user end.

6. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 5 is characterized in that: The flue gas treatment circuit (500) includes a flue gas-third cycle working medium heat exchanger (H7), an NG-flue gas heat exchanger (H4), a flue gas-ice separator (S1), a multi-stage compressor (MC), an LNG-dehydrated flue gas heat exchanger (H3), a dehydrated flue gas-liquid carbon dioxide separator (S2), a cooling tank (W1), a heating tank (W2), a multi-stage expander (ME) and a compensation circuit, wherein: The waste heat flue gas inlet of the heat exchanger (H7) introduces waste heat flue gas caused by natural gas combustion, the normal temperature flue gas outlet of the heat exchanger (H7) is connected to the normal temperature flue gas inlet of the heat exchanger (H4), the dehydrated flue gas outlet of the heat exchanger (H4) is connected to the dehydrated flue gas inlet of the multi-stage compressor (MC), the high pressure flue gas outlet of the multi-stage compressor (MC) is connected to the high pressure flue gas inlet of the cooling tank (W1), the medium temperature flue gas outlet of the cooling tank (W1) is connected to the thermal test inlet of the heat exchanger (H3), the thermal test outlet of the heat exchanger (H3) is connected to the gas-liquid mixed inlet of the separator (S2), the liquid CO2 outlet of the separator (S2) is independently connected to the CO2 storage tank, the residual gas outlet of the separator (S2) is connected to the residual gas inlet of the multi-stage expander (ME), the expanded gas outlet of the multi-stage expander (ME) is connected to the low temperature gas inlet of the heating tank (W2), and the qualified discharge port of the heating tank (W2) is connected to the atmosphere. In the compensation circuit, the multi-stage expander (ME) serves as an electric energy output device, and the electric energy it generates is preferentially supplied to the multi-stage compressor (MC) serving as an electric energy input device.

7. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 6 is characterized in that: In the primary cold energy power generation cycle circuit (100), The LNG-first cycle working medium cold storage heat exchanger (H1) is used to utilize the cold energy of LNG to cool the first cycle working medium, condense the first cycle working medium into a saturated liquid, and simultaneously recover the cold energy of the liquid phase of LNG. When the LNG flow rate is too large, the excess cold energy is stored in the cold storage medium; when the flow rate is too small, the stored cold energy is released to cool the exhaust steam after the first working medium expander (T1) has done work; The first working fluid pump (P3) is used to pressurize the saturated liquid working fluid from the LNG-first circulating working fluid cold storage heat exchanger (H1), thereby increasing the working fluid pressure and providing power for the circulating working fluid to circulate in the system; The first reheater (R2) is used to preheat the working fluid output from the first working fluid pump (P3) by exchanging heat with the superheated steam with a relatively low pressure extracted from the second-stage steam extraction heat recovery branch (102), thereby increasing the working fluid temperature and recovering the heat of the extracted steam; The second first working fluid pump (P4) is used to further pressurize the working fluid after being preheated by the first regenerator (R2) so that the working fluid pressure meets the requirements for entering the second first regenerator (R1) and subsequent circulation, and maintain the circulating pressure of the working fluid in the system; The No. 2 first regenerator (R1) is used to perform heat exchange with the superheated steam with a relatively high pressure extracted from the first-stage extraction steam heat recovery branch (101), preheat the working medium output from the No. 2 first working medium pump (P4), and increase the initial temperature of the working medium; at the same time, the extraction steam is cooled at a constant pressure in the No. 2 first regenerator (R1) and completely condensed; The No. 3 first working medium pump (P2) is used to re-pressurize the working medium after being preheated by the No. 2 first regenerator (R1) to ensure that the working medium can smoothly enter the third circulating working medium-first circulating working medium heat exchanger (H5); The third circulating working medium-first circulating working medium heat exchanger (H5) is used to recover the working medium by utilizing waste heat, heating the first circulating working medium pressurized by the third first working medium pump (P2) into superheated steam, thereby increasing the energy quality of the working medium and preparing for expansion and work in the first working medium expander (T1); a first working medium expander (T1) for causing the superheated steam to expand in the first working medium expander to perform work, converting the internal energy of the steam into mechanical energy to drive a generator for generating electricity; during the expansion process, part of the steam is extracted from different locations for heat recovery; The first stage steam extraction heat recovery branch (101) is used to extract a portion of superheated steam with a relatively high pressure from the first working medium expander (T1), introduce the steam into the second first regenerator (R1) for constant pressure cooling and complete condensation, and the released heat is used to preheat the first circulating working medium after being mixed with the second stage steam extraction heat recovery branch (102) and the first working medium power generation branch (103); The second stage steam extraction heat recovery branch (102) is used to extract a portion of superheated steam with a relatively low pressure from the first working medium expander (T1), enter the first regenerator (R2) for constant pressure cooling, and completely condense. The released heat is used to preheat the condensed first circulating working medium in the first working medium power generation branch (103), thereby further improving the thermal efficiency of the system. The first working medium power generation branch (103) is used to allow the remaining first circulating working medium after the first working medium expander (T1) performs work to continue to participate in the circulation through the first working medium power generation branch (103); In the secondary cold energy power generation cycle circuit (200), The LNG-secondary circulating working medium cold storage heat exchanger (H2) is used to utilize the cold energy of the latent heat section during the LNG gas-liquid phase change to cool the secondary circulating working medium, condensing the secondary circulating working medium into a saturated liquid, thereby realizing the recycling of the cold energy of the LNG latent heat section. When the LNG flow rate is too large, the excess cold energy is stored in the cold storage medium. When the flow rate is too small, the stored cold energy is released to cool the exhaust steam after the second working medium expander (T2) has done work. The No. 1 second working medium pump (P6) is used to pressurize the saturated liquid working medium flowing out of the LNG-second circulating working medium cold storage heat exchanger (H2), increase the working medium pressure, and provide power for the subsequent circulation of the working medium in the system, so that it can smoothly enter the next equipment No. 1 second regenerator (R4); The No. 1 second regenerator (R4) is used to perform heat exchange with the superheated steam with a relatively low pressure extracted from the second-stage steam extraction heat recovery branch (202), on the one hand recovering the heat of this steam to improve energy utilization efficiency, and on the other hand using the recovered heat to preheat the second circulating working fluid output from the No. 1 second working fluid pump (P6) to increase the temperature of the working fluid; The second working medium pump (P7) is used to further pressurize the second circulating working medium after being preheated by the first second regenerator (R4), so that the working medium pressure meets the requirements for entering the second second regenerator (R3) and subsequent circulation, and maintain the circulating pressure of the working medium in the system; The second regenerator (R3) is used to perform heat exchange with the superheated steam with a relatively high pressure extracted from the first-stage extraction heat recovery branch (201), recover the heat of this steam and use it to preheat the second circulating working fluid output from the second working fluid pump (P7), thereby further increasing the initial temperature of the working fluid; The No. 3 second working medium pump (P5) is used to re-pressurize the second circulating working medium after being preheated by the No. 2 second regenerator (R3), ensuring that the working medium can enter the third circulating working medium-second circulating working medium heat exchanger (H6) with sufficient pressure to provide pressure conditions for the subsequent heating process; The third circulating working medium-second circulating working medium heat exchanger (H6) is used to recover the working medium by utilizing waste heat, heating the second circulating working medium pressurized by the No. 3 second working medium pump (P5) into superheated steam, thereby increasing the energy quality of the working medium and enabling it to expand and perform work in the second working medium expander (T2); The second working medium expander (T2) is used for the hot steam to expand and perform work in the second working medium expander (T2), converting the internal energy of the steam into mechanical energy, thereby driving the generator to generate electricity; during the expansion process, part of the steam is extracted from different positions and introduced into the second second regenerator (R3) and the first second regenerator (R4) through the first stage steam extraction heat recovery branch (201) and the second stage steam extraction heat recovery branch (202) respectively, for preheating the second circulating working medium; The first-stage steam extraction heat recovery branch (201) is used to extract a portion of superheated steam with a relatively high pressure from the second working medium expander (T2) and introduce it into the No. 2 second regenerator (R3). In the No. 2 second regenerator (R3), this portion of steam is cooled at a constant pressure and completely condensed, and the heat released is used to preheat the second circulating working medium output from the No. 2 second working medium pump (P7); The second-stage steam extraction heat recovery branch (202) is used to extract a portion of superheated steam with a relatively low pressure from the second working medium expander (T2) and introduce it into the No. 1 second heat regenerator (R4). In the No. 1 second heat regenerator (R4), the steam is cooled at a constant pressure and completely condensed, and the released heat is used to preheat the second circulating working medium output from the No. 1 second working medium pump (P6); The second working medium power generation branch (203) is used to allow the remaining second circulating working medium after the second working medium expander (T2) performs work to continue to participate in the circulation through the second working medium power generation branch (203); In the waste heat recovery circuit (300), The third working medium pump (P8) is used to pressurize the third circulating working medium after being heated by the flue gas-third circulating working medium heat exchanger (H7); The flue gas-tertiary cycle working medium heat exchanger (H7) is used to exchange heat between the high-temperature flue gas generated by natural gas combustion and the tertiary cycle working medium, heating the tertiary cycle working medium and cooling the high-temperature flue gas; The heat exchanger (S3) is used to distribute the high-temperature third circulation working medium to the third circulation working medium-second circulation working medium heat exchanger (H6) and the third circulation working medium-first circulation working medium heat exchanger (H5), thereby cooling the high-temperature third circulation working medium; The third circulating working medium-second circulating working medium heat exchanger (H6) is also used to perform heat exchange between the high-temperature third circulating working medium from the flue gas-third circulating working medium heat exchanger (H7) and the second circulating working medium of the secondary cold energy power generation cycle (200); the second circulating working medium absorbs heat and is heated to superheated steam, thereby increasing its energy quality, and then enters the second working medium expander (T2) to expand and perform work; The third circulating working medium-first circulating working medium heat exchanger (H5) is also used to perform heat exchange between the high-temperature third circulating working medium from the flue gas-third circulating working medium heat exchanger (H7) and the first circulating working medium of the first-stage cold energy power generation cycle (100); the first circulating working medium absorbs heat and is heated to superheated steam, thereby increasing its energy quality, and then enters the first working medium expander (T1) to expand and perform work; In the LNG line (400), LNG pump (P1), used to pressurize low-temperature, low-pressure LNG; The LNG-first circulating medium cold storage heat exchanger (H1) is also used to utilize the cold energy of the liquid phase of the LNG flowing through the LNG pump (P1) to cool the first circulating medium, condensing the first circulating medium into a saturated liquid, thereby transferring cold energy to the first circulating medium and providing a cold source for the first-stage cold energy power generation cycle. It also has a cold energy storage function. When the LNG flow rate fluctuates, it stores excess cold energy and releases it when the LNG flow rate is insufficient, thereby stabilizing system operation. The LNG-secondary circulation medium cold storage heat exchanger (H2) is also used to utilize the latent heat of the LNG flowing through the LNG-first circulation medium cold storage heat exchanger (H1) to cool the secondary circulation medium, condensing the secondary circulation medium into a saturated liquid, thereby transferring cold energy to the secondary circulation medium and providing a cold source for the secondary cold energy power generation cycle. It also has a cold energy storage function. When the LNG flow rate fluctuates, it stores excess cold energy and releases it when the LNG flow rate is insufficient, thereby stabilizing system operation. The NG-flue gas heat exchanger (H4) is used to achieve heat exchange between natural gas and flue gas, that is, using the heat of the flue gas to heat the natural gas. At the same time, the flue gas is cooled during the heat exchange process, and the water in it is cooled into solid ice, thereby removing moisture from the flue gas; The seawater-NG heat exchanger (H8) is used to heat the natural gas using the heat of seawater, ensuring that the output natural gas can enter the user end at an appropriate temperature to meet the user's usage needs; In the flue gas treatment circuit (500), The flue gas-tertiary circulation working medium heat exchanger (H7) is used to recover the waste heat in the flue gas by transferring the heat of the flue gas to the tertiary circulation working medium, thereby increasing the temperature of the tertiary circulation working medium, thereby realizing the recovery and utilization of waste heat and reducing the flue gas temperature; The NG-flue gas heat exchanger (H4) is used to exchange heat between flue gas and natural gas, using the heat of the flue gas to heat the natural gas, thereby increasing the temperature of the natural gas and further reducing the flue gas temperature, condensing the water vapor in the flue gas into solid ice, thereby achieving initial dehydration of the flue gas; The flue gas-ice separator (S1) is used to separate ice particles formed in the flue gas after cooling to prevent the ice particles from entering the subsequent equipment; Multi-stage compressor (MC) compresses the flue gas after preliminary treatment to increase the flue gas pressure; LNG-dehydration flue gas heat exchanger (H3) uses the cold energy of LNG to cool the dehydrated flue gas, further cooling the carbon dioxide in the flue gas and recovering part of the cold energy in the flue gas; The dehydrated flue gas-liquid carbon dioxide separator (S2) is used to separate the liquid carbon dioxide from the cooled flue gas with a capture rate of 99.9%, thereby obtaining carbon dioxide with a purity of 99.9%; The cooling tank (W1) is used to cool the incoming dehydrated flue gas. The cooling medium is water, and the heated water is supplied to the hot end users. The multi-stage expansion stage (ME) is used to expand the remaining gas after the carbon dioxide is separated in the multi-stage expansion stage to do work. Through the expansion of the gas, the internal energy of the gas is converted into mechanical energy, thereby driving other equipment or generating electricity; The heating tank (W2) is used to heat the remaining gas to room temperature and then discharge it into the atmosphere. The heating medium is water, and the cooled water is supplied to the cold end users.

8. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 7 is characterized in that: The LNG-first circulating working medium cold storage heat exchanger (H1) and the LNG-second circulating working medium cold storage heat exchanger (H2) both comprise a shell (601), a heat transfer tube bundle (602), a support assembly (603), a cold storage medium (604) and a circulating working medium. The support assembly (603) is fixedly mounted in the shell (601), and the heat transfer tube bundle (602) is fixedly mounted on the support assembly (603). The shell (601) is filled with the cold storage medium (604) and the circulating working medium. The cold storage medium (604) is immersed in the circulating working medium. When the flow rate of the low-temperature natural gas in the heat transfer tube bundle (602) is too large, the additional cold energy is stored in the cold storage medium (604). When the flow rate of the low-temperature natural gas in the heat transfer tube bundle (602) is too small, the cold energy stored in the cold storage medium (604) is used to cool the exhaust steam after expansion and work in the expander in the cold energy power generation cycle where the cold storage medium (604) is located. The circulating working medium in the LNG-first circulating working medium cold storage heat exchanger (H1) is the first circulating working medium (605), and the heat transfer tube bundle (602) in the LNG-first circulating working medium cold storage heat exchanger (H1) contains liquefied natural gas pressurized to a vaporization pressure by an LNG pump (P1); The circulating working medium in the LNG-second circulating working medium cold storage heat exchanger (H2) is the second circulating working medium (606), and the heat transfer tube bundle (602) in the LNG-second circulating working medium cold storage heat exchanger (H2) contains natural gas that has been heated by the LNG-first circulating working medium cold storage heat exchanger (H1) but still has a relatively low temperature. The arrangement of the heat transfer tube bundle (602) includes but is not limited to in-line, spiral, serpentine, sleeve, and fin types; The cold storage medium (604) includes but is not limited to rock, metal, alloy or a combination of any two or three of rock, metal and alloy.

9. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 8 is characterized in that: The first circulating working medium (605) and the second circulating working medium (606) include C2H4, C2H6, C3H6, C3H8, C4H 10 , CH3F, CH2F2, CHF3, C2H4F2, C2H3F3, C2H2F4, C2HF5, C2F6, C3F8 and mixtures of two or more.

10. The adaptive zero-carbon power generation system utilizing LNG cold energy and flue gas waste heat according to claim 9 is characterized in that: In the first-stage cold energy power generation cycle (100), the steam extraction amount is determined by the following formula: α1(h a1 -h a1′ )=(1-α1)(h a1′ -h b1″ ) α2(h b1 -h b1′ )=(1-α1-α2)(h b1′ -h c1 ) where h a1 、h a1′ 、h b1 、h b1′ 、h b1″ 、h c1 are the enthalpy values ​​of points a1, a1′, b1, b1′, b1″, and c1, respectively, thereby obtaining the steam extraction amount α1 of the first-stage steam extraction heat recovery branch (101): The extraction steam volume α2 of the second stage extraction steam heat recovery branch (102): Then the steam quantity of the first working medium power generation branch (103) is (1-α1-α2); The specific steam extraction amount of the secondary cold energy power generation cycle circuit (200) is determined by the following formula: β1(h a2 -h a2′ )=(1-β1)(h a2′ -h b2″ ) β2(h b2 -h b2′ )=(1-β1-β2)(h b2′ -h c2 ) where h a2 、h a2′ 、h b2 、h b2′ 、h b2″ 、h c2 are the enthalpy values ​​of points a2, a2′, b2, b2′, b2″, and c2, respectively, thereby obtaining the extraction steam volume β1 of the first-stage extraction steam regeneration branch (201): The extraction steam volume β2 of the second stage extraction steam regeneration branch (202): Then the steam quantity of the second working medium power generation branch (203) is (1-β1-β2).

Images